The loss or reduction in lung function in patients with cystic fibrosis (CF) is associated with increased mortality and varies between individuals and over time. The management of these patients would be improved if lung function decline or imminent pulmonary exacerbations could be predicted or detected at an early stage. The number and severity of pulmonary exacerbations influence the final outcome of the disease by speeding up the overall deterioration of the patient. Exacerbations are defined by acute onset of pulmonary symptoms such as breathlessness, increased coughing, changes in the color of sputum and loss of appetite and weight. Detection of the acute onset of these pre-clinical symptoms would avoid costly and unnecessary hospitalization for intravenous (IV) antibiotic therapy by allowing timely non-emergency intervention by the clinician or other healthcare professional.
Several techniques have been published which purport to aid the clinician in assessing the pulmonary status of patients with cystic fibrosis, often involving spirometry parameters and chest x-ray scores. In the case of “Pulmonary Outcome Prediction for Cystic Fibrosis Patients” by Kraemer, R. and Thamrin, C. Pediatr Pulmonol 45: 1153-1155, 2010 a complex, composite score is derived from retrospective data. Some techniques, such as that shown in EP 2245985, involve the use of specific respiratory equipment, primarily for use with patients with Chronic Obstructive Pulmonary Disease (COPD). Other more general techniques for the monitoring of clinical episodes have been described which involve measuring a number of physiological parameters and various biological markers have been identified that could be used for detecting exacerbations.
Given that patients with cystic fibrosis may infrequently visit clinics and have long periods in which they self-manage their condition whilst leading normal active lives, exacerbation detection techniques cannot rely on ‘old’ data taken during previous clinical visits, neither can they wait until the next routine hospital visit.
Therefore, there is a need for an improved method and system for determining an indication of the lung function of the patient. In particular, it is desirable to be able to derive the indication of the lung function from parameters that are obtainable from apparatus that can used in the home environment of a patient. It is also desirable to provide an early indication of when the lung function of the patient is deteriorating.